Phosphonoether carboxylates

ABSTRACT

Phosphonoether carboxylate esters and acids are intermediates for phosphonoether carboxylate salts useful as sequestering agents.

BACKGROUND OF THE INVENTION

This invention relates to novel phosphonoether carboxylates. The estersand acid forms of the compounds are useful as intermediates to saltsuseful as sequestrants for various metal and alkaline earth metal ions(particularly ions such as calcium and magnesium ions which contributeto water "hardness").

The value of sequestrants in various industrial and domestic watertreating and cleaning applications is well understood by those skilledin the art. It is further recognized that the provision of novelsequestering agents to permit selection of optimum sequesteringcompounds and formulations for particular applications is a continuingneed of the art.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide novel sequestrantcompounds and novel intermediate compounds useful for preparing suchsequestrants.

The compounds by which this objective is achieved are phosphonoethercarboxylates whose structure, synthesis and use will be understood fromthe following description of the preferred embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The ester forms of the compounds of the present invention can berepresented by the formula ##STR1##

In the above formula, R represents benzyl, or an alkyl group containingfrom 1 to 4 carbon atoms; R_(I) represents hydrogen, an alkyl groupcontaining from 1 to 3 carbon atoms, CH₂ PO₃ R₂ or CH.sub. 2 COOR;R_(II) represents hydrogen, an alkyl group containing from 1 to 3 carbonatoms, CH₂ COOR, CH₂ PO₃ R₂ or COOR; R_(III) represents hydrogen, analkyl group containing from 1 to 3 carbon atoms, CH₂ COOR or CH₂ PO₃ R₂; and R_(IV) represents hydrogen, an alkyl group containing from 1 to 3carbon atoms, CH₂ PO₃ R₂, CH₂ COOR or PO₃ R₂. At least one of R_(I),R_(II), R_(III) and R_(IV) must be COOR, CH₂ COOR, PO₃ R₂ or CH₂ PO₃ R₂.

Preferred compounds of the invention are those in which R_(I) ishydrogen, an alkyl group containing 1 to 3 carbon atoms or CH₂ COOR;R_(II) is hydrogen, an alkyl group containing 1 to 3 carbon atoms, CH₂COOR or COOR, R_(III) is hydrogen, an alkyl group containing 1 to 3carbon atoms, or CH₂ PO₃ R₂ ; and R_(IV) represents hydrogen, an alkylgroup containing from 1 to 3 carbon atoms, CH₂ PO₃ R₂ or PO₃ R₂.

These compounds can be prepared by a Williamson ether type synthesisreacting: ##STR2## where X in one reactant is -O alkali metal and in theother is -Cl or -Br.

Alternatively, compounds wherein one of R_(I) and R_(II) is CH₂ COOR orone of R_(III) and R_(IV) are CH₂ PO₃ R₂ may, in some instances, be morereadily prepared by a Michael-type Addition to a double bond of anappropriate unsaturated starting material.

For example: ##STR3## This is particularly preferred when R_(I) is CH₂COOR.

Similarly, the reaction ##STR4## is preferred when R_(IV) is CH₂ PO₃ R₂.

Conversion of the ester forms of the compounds to acid forms isaccomplished by acidulation with a strong acid, e.g. HCl, H₂ SO₄, etc.The alkali metal, ammonium or amine salt forms can be obtained byneutralization of the acids or by reacting the ester with a strong base(saponification). The tendency of substituted malonates to undergo##STR5## decarboxylation during long acid hydrolysis conditions makesconversion of such ester to the corresponding acid form somewhatdifficult. This difficulty may be avoided by hydrolysis of compoundscontaining such malonate ester groups under basic conditions ofhydrolysis (saponification) to obtain the salt form directly. Since oneof the R groups in the -PO₃ R₂ ester moiety is resistant tosaponification, in some instances partial ester salts can be obtained.It is noted, however, that such partial salts containing oneunhydrolyzed ester groups per phosphorus have useful sequesteringproperties, even though the fully hydrolyzed compounds are usuallypreferred. Fully neutralized salt forms of the compounds can often beconveniently obtained by hydrogenation of benzyl ester forms ##STR6## ofthe compounds in the presence of a palladium on charcoal catalystfollowed by neutralization of the hydrogenated product with a base.

As indicated, the total or partial salt compounds of the invention aresequestrants which can be used in conventional manner in a variety ofapplications. For example, such sequestrants are useful as watersofteners and, in some instances, as scale inhibitors or as detergencybuilders. The invention is further illustrated by the followingexamples:

EXAMPLE I

A solution of 38 gms of ##STR7## in 150 ml. bis (2-methoxy ethyl) etheris prepared by reacting 0.2 moles of diethylphosphite with 0.2 molessodium in bis (2-methoxyethyl) ether and adding 0.2 molesparaformaldehyde. About 51 gms of ##STR8## is then added to the solutionover a period of about 1/2 hour, the temperature being maintainedbetween 25°-30° C. The mixture is then refluxed for one hour, allowed tostand about 16 hours, and filtered. The filtrate is distilled, theproduct ##STR9## being obtained at 114°-121.5° C., 0.05 mm Hg. Theproduct is a colorless liquid having a refractive index, n_(D) ²⁰ 1.4381and exhibiting the nuclear magnetic resonance spectrum shown in table 1following the examples.

0.05 moles of the above ester is reacted with 0.15 moles of NaOHsolution followed by evaporation to dryness. The product obtained is thepartial ester salt. ##STR10##

The above salt is tested for sequestration function (according to theprocedure described by Matzner et al., Tenside, 10, 119-25; 239-245(1973)) and found to effectively sequester calcium ions.

EXAMPLE II

A solution of 48 gms ##STR11## in 150 ml. bis (2-methoxy ethyl) ether isprepared by reacting 0.2 mole diisopropylphosphite, 0.2 mole sodium, and0.2 mole paraformaldehyde. About 51 gms ##STR12## is added to thesolution over a period of about 20 minutes while maintaining thetemperature at about 35° C. The mixture is then refluxed for 2 hours,allowed to stand about 16 hours, and filtered.

Solvent is distilled from the filtrate which is then again filtered toremove precipitated solids. The filtrate product ##STR13## is a clearliquid having the nuclear magnetic resonance spectrum shown in table 1following the examples.

About 9.2 grams of the above ester product is added to 3 grams sodiumhydroxide in 110 ml. ethanol and the mixture is refluxed for 10 hours.The alcohol is then evaporated from the mixture, the residue dissolvedin water, and dimethylformamide added. After 48 hours, white crystals of##STR14## product salt precipitate. The product salt exhibits thenuclear magnetic resonance spectrum shown in table 1 following theexamples and, when tested for sequestration function according to theprocedure referenced in Example I, is found to effectively sequestercalcium ions.

EXAMPLE III

About 0.2 mole maleic acid diethyl ester is added to a solution of 0.2mole ##STR15## dissolved in 100 ml. bis (2-methoxy ethyl) ether, themixture being maintained at about 25° C. The mixture is refluxed for 4hours, treated with 0.2 mole acetic acid and distilled to separate##STR16## as a colorless oil.

The above ester product is hydrolyzed by reflux with concentratedhydrochloric acid for 8 hours to yield ##STR17## The salt of this acidobtained by neutralization with sodium hydroxide is found to effectivelysequester calcium ions when tested according to the procedure referencedin Example I.

EXAMPLE IV

About 0.1 mole of ##STR18## is slowly added to 0.1 mole of ##STR19## in50 ml. bis (2-methoxy ethyl) ether and the resulting mixture is refluxedfor 3 hours. Precipitated NaBr is separated and the filtrate distilledto separate ##STR20## product.

This product is hydrolyzed by refluxing in concentrated hydrochloricacid for 10 hours to yield the acid ##STR21## The salt obtained byneutralization of the above acid is an effective sequestrant for calciumions.

EXAMPLE V

A solution of 0.5 mole ##STR22## in tetrahydrofuran is added to 0.5 moleethene -1,2 - diphosphonate - ethylester. The resulting mixture isrefluxed for 10 hours, treated with 0.5 mole acetic acid and distilledto separate the ester product ##STR23## This ester product is hydrolyzedby refluxing in concentrated hydrochloric acid to yield the acidproduct.

The salt of the above acid product obtained by neutralization withsodium hydroxide is an effective sequestrant for calcium ions.

EXAMPLE VI

About 0.2 moles ##STR24## is slowly added to a solution of 0.2 moles##STR25## in 150 ml. bis (2-methoxy ethyl) ether while maintaining thetemperature at about 35° C. The mixture is then refluxed for 2 hours,allowed to stand 16 hours, and filtered. Solvent is distilled from thefiltrate to leave a clear liquid ester product ##STR26##

This ester product is dissolved in ethanol and hydrogenated in thepresence of a palladium on charcoal (5% by weight palladium) catalyst.The catalyst is separated by filtration and ethanol evaporated leavingthe acid product ##STR27## Reaction of this acid product with sodiumhydroxide in ethanol (2 hours reflux) and evaporation of the ethanolyields the salt product ##STR28## as a white solid. This salt product isan effective sequestrant.

Table I below shows nuclear magnetic resonance spectra of representativecompounds of the invention.

In the table, coupling constants (J with subscripts indicating specificnuclei coupled) are expressed in hertz; H represents proton count; t,d,and qu, respectively, indicate triplets, doublets and quadruplets.

    __________________________________________________________________________    PHOSPHORUS-31-AND HYDROGEN-1-NMR SPECTRA IN PPM                               (.sup.1 H-NMR - trimethyl silane reference)                                   __________________________________________________________________________                         a         b      c         d      e                      __________________________________________________________________________     ##STR29##           1.28 (t)  1.57(s,2.85H)                                                                        3.87(d,J.sub.PCH 10.8)                                                                         4.21 (qu)              a'dcbeaCCl.sub.4     a':1.32 (t).sup.12H                                                                     c + d + e = 10.1H                                                                              4.07                                                                          (2 qu)                                             1.5(t,6.1H)                                              Eu(DPM).sub.3                                          4.50                                        a':2.68(t,6.02H)                  (qu,4.05H)              ##STR30##                                             4.7                    aecbdaCCl.sub.4      1.30      1.55(s,2.7H)                                                                         3.78(d,J.sub.PCH 10.6)                                                                  4.2(qu)                                            (m,18.7H)                                                                               c + d + e = 7.6H                                ##STR31##           1.25(d,J6: 6.08H)                                                                       1.47(s,2.95H)                                                                        3.47(d,J11: 2.08H)                                                                      4.5 (m,0.86H)                 adcbD.sub.2 O                                                                                      (.sup.31 P-NMR - 85% H.sub.3 PO.sub.4 reference)          ##STR32##                                 -19.0 (subst.)                     a'dcbeaCCl.sub.4                                                               ##STR33##                                 -17 (subst.)                       aecbdaCCl.sub.4                                                                ##STR34##                                 -17.5 (in H.sub.2 O)               adcbD.sub.2 O                                                                 __________________________________________________________________________

What is claimed is:
 1. A compound represented by the formula: ##STR35##wherein R is selected from the group consisting of alkyl groupscontaining from 1 to 4 carbon atoms and benzyl; R_(I) is selected fromthe group consisting of hydrogen, alkyl groups containing from 1 to 3carbon atoms, and CH₂ COOR; R_(II) is selected from the group consistingof hydrogen, alkyl groups containing from 1 to 3 carbon atoms, CH₂ COORand COOR; R_(III) and R_(IV) each are selected from the group consistingof hydrogen, alkyl groups containing from 1 to 3 carbon atoms and CH₂COOR; at least one of R_(I), R_(II), R_(III), and R_(IV) being COOR orCH₂ COOR.
 2. A compound according to claim 1 wherein R is benzyl.
 3. Acompound according to claim 2 wherein R_(I), R_(III) and R_(IV) arehydrogen.